Radio system



June 17, 1941. c, J E N ETAL 2,245,660

RADIO SYSTEM Filed 001:. 12, 1938 7 Sheets-Sheet 1 FIG./

Amy AXIS BA ARTIFICIAL FHA 55 SHIFT'ERS AZIMUTH k/7 lunch- RECEIVER FIG.IA

ar/o5 VERTICAL mus:

I I llllllfl AZ/MUTHAL PLANE VIE VERTICAL PLANE VIE W III INVENTORS:DMAN A TTORNEY June 17, c B H. FELDMAN ETAL RADIO SYSTEM Filed Oct. 12,1938 '1 Sheets-Sheet 2 FIG. 2

AZIMU TIMI. FLA NE VIE W VERTICAL PLANE VIEW //v l/EN TOPS: fiDMA NATTORNEY Jun 17, 1941.

COUPLERS FIG. 3

PHASE SHIFTER c. B. H. FELDMAN ETAL 2,245,660

RADIO SYSTEM 7 Shets-Sheet 5 Filed Oct. 12, 1938 COUPLERS CBHFELDMAN H.Z'FR/IS A TTOR/VE V IN [/5 N TOPS:

J1me 1- c. B. H. FELDMAN EIAL 2,245,660

RADIO -SYSTEM Filed Oct. 12, 1938 7 Sheets-Sheet 4 .QBH. FELDMA/V j 'H.TTFR/IS ATTORNEY June 17, 194 c. B. H. FELDMAN ETAL 2,245,660

RADIO SYSTEM Filed Oct. 12, 1938 '7 Sheets-Sheet 6 .C.B.H. FELDMANINVENTORS. H ZFRIIS ATTORNEY Patented June 17, 1941 RADIO SYSTEM Carl B.H. Feldman and Herald '1'. Friis, Bumaon, N. .L, assirnors to BellTelephone Laboratories,

Incorporated, New York, N. 1., a corporation of New York ApplicationOctober 12, 1938, Serial No. 234,562

12 Claims.

This invention relates toradio communication systems and moreparticularly to methods of and means for obtaining controllable andsharp directive transmission and/or reception in such systems.

As disclosed in Patent 2,076,222 to E. Bruce, April 16, 1937, and Patent2,041,600 to H. T. Friis, May 19, 1936, it has been proposed to improveradio communication, especially with respect to signal-to-static ratioand fading, by aligning in a given plane, as for example, the verticalor great circle plane containing two widely separated radio stations,the direction oi maximum antenna reception at one of two widelyseparated cooperating stations and the direction of maximum antennatransmission at the other station, with the optimum transmission pathbetween the stations, that is, with the path followed by the strongestof the, several incoming waves. It has also been proposed to improveradio communication by confining the reception, assuming diversityoperation is not employed, to a single maximum incoming wave regardlessof the number oi wavesestablished at the receiving station by thetransmitting station. 1 While, in long range communication systems, thedirectional changes oi the maximum wave are usually greatest and mostfrequent in the great circle or vertical plane-directional changes inthis wave also occur in the horizontal or azimuthal plane. It thereforeappears desirable to align or steer, independently in these two planes.the directions of maximum action of the receiving antenna ortransmitting antenna or both. Moreover, it now appears that improvedtwo-point communication may also be obtained by utilizing at thetransmitting station an antenna system having a steerable azimuthaldirective characteristic and a wide range nonsteerable verticaldirectional characteristic and,

It is a further object of this invention to secure an antenna arrayhaving a sharp, steerable directive characteristic in one plane and abroad nonsteerable directive characteristic in a plane perpendicularlyrelated thereto.

It is still another object of this invention to align in a two-pointcommunication system, the

'maximum direction of action for a transmitting or a receiving antennaarray with the optimum transmission path between the cooperatingstations,-regardless of the orientation or angle with respect to thehorizontal or vertical, of the optimum path.

According to one embodiment of the invention the transmitting orreceiving antenna comprises a plurality of end-on antenna subarrayspositioned in a broadside array or a plurality of broadside subarrayspositioned in an end-on arrays, each subarray comprising spaced antennaunits and having a steerable space factor diagram or directionalcharacteristic. The "space factor characteristic is termed the arraycharacteristic in the above-mentioned Friis patent and is here definedas a portion of the complete directive characteristic of a systemcomprising a plurality of spaced antenna units, the shape and size ofthe space factor characteristic for a given direction of transmission orreception being independent of the directive characteristic of eachantenna unit and a function of the number of antenna units, the spacingtherebetween and the phase relation of the currents in the antennaunits. The several subarray characteristics are preferablysimultaneously steered or controlled by means of a uni-control knob andthe outputs of the several subarrays are connected to a common receiverthrough individual adjustable phase shifters controlled by a seconduni-control knob.

Assuming end-son subarrays arranged in broadside are utilized, themaximum directional cones of the similar space factor directivecharacteris- I tics for the end-on subarrays are similarly positioned,that is, in effect, superimposed to-form an effective subarray or end-oncone and also so positioned or steered that the longest axis of theefiective subarray cone coincides with the direction of the maximumincoming wave or the desired direction of the outgoing wave. The flatdisc or the maximum shallow cone of the broadside space factor is alsosteered so as to align with the above-mentioned direction. The efiectivesubarray cone and the broadside cone or disc have a common apex and axesperpendicularly related in the azimuthal or ground plane, whereby thecone and the disc intercept or coextend in space to form anexceedingly-sharp cigar-shaped or resultant lobe which may be steered,independently, in the azimuthal and vertical planes and which may beadjusted easily to align with any direction whatsoever incoming oroutgoing with respect to the antenna system. If broadside subarraysarranged in an end-on array are employed, the procedure is similar, thebroadside fiat cones being superimposed to form an efiective broadsidedirective disc or shallow cone. Vifhile antenna units each having anondirectional directional characteristic may be used, directional unitsare preferably employed. The lobes of the directional units should besuperimposed to form an effective unit lobe, and

positioned so as to include the normal azimuthal and vertical angularranges and to coextend with the two space factor cones.

Steerabie antenna systems, as described above, may be used at each ofthe stations constituting a two-point communication system. Satisfactoryperformance may also be obtained by utilizing at the transmittingstation an array arranged for azimuthal steering and comprising antennaunits having a relatively broad vertical directional characteristic andby utilizing at the receiving station an array arranged for verticalsteering and having a non-directional or a relatively broad horizontalor azimuthal directional characteristic.

The invention will be more fully understood from a perusal of thefollowing specification taken in conjunction with the drawings on whichlike reference characters denote elements of similar function and onwhich:

Fig. 1 illustrates an azimuthal plane steerable antenna systemcomprising a broadside antenna array; and Figs. 1A and 13, respectively,illustrate the vertical and azimuthal directional characteristics of thesystem of Fig. 1;

Fig. 2 illustrates a broadside antenna array which may be substitutedfor the array included in the system illustratedby Fig. l; and Figs. 2Aand 2B illustrate, respectively, the vertical and azimuthal directivecharacteristics of the system of Fi 2;

Fig. 3 illustrates an antenna system arranged for independent horizontaland vertical directional steering and comprising non-directive units;Figs. 3A, 3B and 3C illustrative, in perspective, the solid adjustabledirectional characteristic of the system of Fig. 3, and Figs. 3D, 3E, 3Fand 3G are cross-sectional views of the solid characteristic asillustrated by Fig. 3A;

Fig. 4 illustrates an alternative arrangement for steering, horizontallyand vertically, the directional characteristic of the array of Fig. 3;

Fig. 5 illustrates an array comprising directional units which may besubstituted for the array included in each of Figs. 3 and 4, Fig. 5Aillustrates the solid directional characteristic of Fig. 5 and Figs. 53,5C and 5D are cross-sectional views of the solid characteristicillustrated by Fig. 5A;

Fig. 6 illustrates an antenna system having a wide non-steerableazimuthal characteristic and arranged for vertical steering; Fig. 6Aillustrates the solid directional characteristic of the system of Fig. 6and Figs. 6B and 6C are crosssectional views of the solid characteristicillustrated by Fig. 6A;

Fig. 7 illustrates a two-point communication "system arranged forcooperative steering; and

Figs. 7A and 7B illustrate, respectively, the azimuthal and verticalplane steerable characterlstics of the two-point communication systemillustrated by Fig. 7.

Referring to Fig. 1, reference numerals I designate unidirective rhombicantennas of the type disclosed in the copending application of E. Bruce,Serial No. 513,063, filed February 3, 1931, the rhombics being spaced onthe broadside axis BA", and the spacing being determined by the spacefactor desired, as disclosed in the above-mentioned Friis patent. Therhombic antenna size and the spacing may be such that the units overlap(as illustrated) in which case the units are preferably also spacedvertically in a staggered manner, the spacing being sufllcient tominimize mutual coupling.

Numerals 2 designate antenna couplers one of which is included betweeneach of the balanced lines 3 connected to the rhombic antennas I and theassociated unbalanced coaxial line 4. The rhombic antenna units areconnected by means of the coaxial lines 4 and 5 to the common receiver6, all except one of the two extreme rhombic units being connected tothe receiver 6 through individual adjustable phase shifters I.Artificial lines 8 are inserted in the intermediate coaxial lines 4 forthe purpose of rendering the coaxial lines equal in electrical length.Preferably. the first detectors of the receiver are connected betweenlines 4 and 6, the coaxial lines 4 being radio frequency lines and thesingle conductor lines 5 being intermediate frequency lines. Asdisclosed in the above-mentioned Friis patent the phase shifters areactuated by knob 9 and shaft i0 through an assembly of uniformly gradedgears II and equal size gears I2, whereby the phase difference betweenthe currents in every pair of adjacent units may be ad- Justed to thesame desired amount. Considering the extreme right-hand rhombic antennaunit as a reference point, rotating the knob 9 in one direction, as forexample, clockwise, in the direction of the arrow l3, retards the phasesof the remaining antenna currents with respect to that of the referenceantenna, whereas rotating the knob counter-clockwise in the directionI4, advances the phases of the remaining antenna current with respect tothat of the reference antenna.

Referring to Figs. 1A and 13, area I5 represents the vertical planeintersection, and area I6 the projection on a. horizontal plane of thesolid uni-directive maximumlobe, of each rhombic antenna unit, theseveral whale-shaped unit maximum lobes being considered superimposedand forming an effective unit lobe represented by the same areas I5, I6.The effective uni lobe is positioned so that it includes the normalangular directive range in both the vertical and azimuthal planes of thedesired or maximum wave. Assuming the phase shifters I are ad- Justed toproduce in-phase antenna currents, the maximum portion or section of thebroadside space factor characteristic is wheel or discshaped and alignedwith direction I1 included in the great circle plane. Area I8illustrates the vertical plane section and area I9 the horizontal planesection of the broadside space factor disc for this particularadjustment. As indicated in Patent 2,041,600 mentioned above, the

superimposed broadside array disc I 8, I9 and.

the effective unit lobe I5, I6 combine to give a s arp resultant lobe,the vertical plane section of which is illustrated by area 20 and theazimuthal plane section by area 2|. When the phase shifters I areadjusted by means of knob 9 to produce out-of-phase currents, the discor wheel-shaped space factor changes to a shallow cone. The resultantlobe for the system is then aligned with a direction making an anglewith a great circle plane, the shallow cone and the resultant lobe beingshifted to the left of the great circle plane upon, for example,clockwise rotation of knob 9 and to the right upon-counterclockwiserotation. In Figs. 1A and 13 areas 22 and 23 shown in dotted linesrepresent, respectively, the vertical plane and the azimuthal planesections of the broadside shallow directive cone when the system isadjusted for alignment with direction 26; and numerals 24 and 25illustrate, respectively, the corresponding intersections 01' theresultant array lobe.

It will thus be seen that the system of Fig. 1 provides a widehorizontal steering range and that electrical steering in the azimuthalplane, over equal ranges on both sides of the great circle plane, or themaximum direction of radiant action of the system, may be easilyaccomplished by manipulating the uni-control knob 9. If the prevailingazimuthal direction is not in the great circle plane, the broadsidearray axis may be positioned perpendicular to the vertical planecontaining the direction whereby the steering range may be centered onthe'prevailing azimuthal direction. For example, in transatlanticcommunication, it hasbeen round that the azimuthal direction is usuallyseveraLdegrees south of the great circle plane and that a moresatisfactory steering range may be obtained by constructing orpositioning the array so that its steering range is centered on theprevailing southern direction.

Of course, any number of rhombic unit antennas may be utilized in asystem of Fig. 1 and the units may be uni-directive, or directive unitsof a type other than the rhombic type. It should be noted that, whilemanipulation of knob 9 alters the projection of the maximum array coneor disc on the horizontal and vertical planes, an array containingbroadside directional units having their maximum lobes aligned with theinphase disc-shaped space factor characteristic (as illustrated by Figs.1, 1A and 1B) is primarilyadapted for horizontal or azimuthal steering,whereas an array containing end-on units having their maximum lobesaligned with a sharp or small angle cone space factor characteristicproduced by out-oi-phase currents is primarily adapted for steering inthe vertical or great circle plane, as indicated by Fig. 10' of theFriis Patent 2,041,600 mentioned above.

A wider horizontal steering range may be ob tained by replacing thearray illustrated in Fig. 1

with the array illustrated by Fig. 2 and comprising vertical antennas.Referring to Figs. 2,

an in all except one of the conductors b.

2A and 2B, reference numerals 21 designate vertical antenna elementsarranged to form six circular antenna cages 28. The top extremities ofthe elements 21 of each cage may be connected together or left free andthe bottom extremities are connected to the inner conductor of theassociated coaxial line 4. The apparatus connected to the six cages isthe same as that illustrated below the line X--X in Fig. 1. 7

Assuming each cage is 9. half wave-length high, each cage isnon-directive in the azimuthal plane and bilateral in the verticalplane, the vertical plane and azimuthal directional characteristics ofeach cage being represented, respectively, by the areas 29 and 30. As inFigs. 1A and 13, areas 18 and I9 illustrate, respectively, theintersections of thegreat circle plane and the azimuthal plane with thedirectional space factor disc for the array, the phase shifters I beingadjusted for direction i1. Numerals 3| and 32 designate, respectively,the areas produced by the intersections of the resultant directionallobe of the system with the great circle and azimuthal planes. Bymanipulating knob 9 the array disc may be changed to a shallow cone andadjusted to the position illustrated by areas 33 and 34. The resultantlobe for the system assumes the vertical plane. position represented byarea 35 and the azimuthal position represented by area 36. As in I thesystem of Fig. 1 the shallow array cone and resultant lobe may besteered to the right or left or the great circle axis 31 by properrotation of knob 9. Thus a 360 degree azimuthal steering range and anextremely wide vertical range are obtained by means of the system ofFig. 2. This particular arrangement is admirably suited for ascertainingthe horizontal arrival direction of vertically polarized wave componentsin a twopoint communication system. While Fig. 1 and Fig. 2 have beendescribed as receiving systems, obviously in place of the receiver 6,and associated first detectors, a transmitter may be employed and thedirection of transmission may be aligned with any desired path. Anypractical number of cages may be employed.

Referring to Fig. 3, reference numerals 38 designateantenna-counterpoise units each comprising a doublet antenna, andnumerals 2, 3 and 8 designate respectively antenna couplers, balancedlines and coaxial lines as already described in connection with Fig. 1.The antenna units are arranged, with respect to the direction 39 inthree end-on subarrays til, ti and 42; and the three subarrays arearranged in a broadside array. Considering any of the subarrays 40, 45and 42, all of the antenna units are connected by means of theassociated coaxial lines 4 and a single conductor line b to a commonline conductor 43, individual adjustable phase shifters i being includedAs in Fig. 1 the first detectors (not illustrated) of the receiver arepreferably included between the coaxial lines t and the single conductorline 5, the coaxial lines 8 being radio frequency lines and the singleconductor lines 5 being intermediate frequency lines. As disclosed inthe above-mentioned Friis patent the adjacent coaxial lines differ inlength an amount equal to the spacing between the antenna units. As alsoexplained in Patent 2,041,600 in the case of each of subarrays 60, lland d2 one phase changer is driven directly, and the remaining phasechanger indirectly through a gear assembly M, by shaft 45 and associateduni-control knob 46. Knob dB is common to the several end-on subarrays,whereby the currents in the adjacent units, in each subarray, may beadjusted to the same desired phase difierence and the three end-onsubarray cones may be simultaneously adjusted or steered.

Conductor 43 from one of the subarrays, preferably but not necessarilythe central subarray in a system comprising an odd number of subarrays,as illustrated, is connected directly, and

i the remaining conductors 43 connected through adjustable phaseshifters 51, to the common receiver 48. The phase shifters 41 areadjusted by means of knob 49 and associated shafts 50 and 5| which areconnected together through a differential gear assembly 52, whereby asexplained in the copending application or N. J. Pierce and F. A.Polkinghorn, Serial No. 149,824, filed June 23, 1937, they rotate inopposite directions and currents of the same phase diilerence areobtained from the adjacent antennas. The phase shifters 41 are connectedtoshafts 50 and it through equal size driving gears 53 and equal sizedriven gears 54.

In the system of Fig. 3, each end-on may comprise any practical numberof antenna units and the broadside array may comprise any practicalnumber of end-on subarrays. If additional antenna units are provided ineach subarray, the additional phase shifters required should beassociated with shaft 45 through a uniformly graded gear arrangement asdisclosed in subarray the above-mentioned Friis patent. Again, if twoadditinal end-on subarrays are provided, the additional phase shifters55 required are preferably connected to shafts 50 and 6| through auniformly graded gear arrangement 66 comprising driven gears 54 of thesame size as gear 84 and driving gears equal to each other but largerthan driving gears 58.

Referring to Fig. 3A, the operation of the system will now be described,it being assumed that the system is used for reception and that thephase shifters 41 produce in-phase currents from the subarrays 40, 4iand 42. The line X included in the ground plane and in the verticalgreat circle plane XOZ, represents the end-on array axis and the line YOincluded in the vertical plane YOZ represents the broadside array axisof the system of Fig. 3, the plane YOZ being perpendicularly related tothe plane XOZ. The hollow cone 51 having a wall I58 represents oneposition of the effective subarray maximum directive cone of the end-onspace factor characteristic and the wheel or disc 59 having a thicknessor wall 60 illustrates the maximum section or sector of the broadsidespace factor characteristic. The end-on and the broadside space factorcharacteristics have a common origin 0 and perpendicularly related axescoincident, respectively, with the end-on axis X0 and the broadside axisYO. As is evident, the two space factors coextend or coexist in thespace or volume bounded in part by the surface BI and they multiply orcombine to produce the cigar-shaped resultant lobe 62. The resultantlobe has a longitudinal axis 63 included in the great circle or verticalplane XOZ, a length equal to the product of the two space factors and acrosssection shape similar to surface 6|. The endon space factor phaseshifters and the broadside space factor phase shifters are adjusted sothat the axis 63 is aligned with the direction 64 of the strongestincoming wave, this direction being included in the great circle planeand also included in the vertical plane wave cluster 65 and th azimuthalplane wave cluster 88. The number of units and/or the spacingtherebetween along the two axes may be the same or different; and theend-on and broadside space factors may be the same, or they may differconsiderably.

Fig. 3D is a cross-sectional view of the solid representation of Fig.3A, as seen when one looks at the vertical plane XOZ; Fig. 3E across-sectional view seen when one looks at the horizontal plane XOY;Fig. 3F a cross-sectional view as seen when one looks at the obliqueplane containing the lobe axis 63 and the broadside axis CY, and thefull line representation included in Fig. 3G is a view looking alongaxis 83 at the surface BI and toward the center or origin 0. As in 'Fig.3A, numerals 61, 58 and 62 designate, respectively, the end-on spacefactor cone, the broadside space factor disc and the resultantcigar-shaped lobe. In Fig, 3F the dot-dash line indicates theintersection of the end-on cone with a horizontal plane.

Assuming it is desired to align the axis 63 of the system lobe 62 withanother direction as, for example, a direction represented by one of thearrows shown in Fig. 3A, and other than direction or arrow 64, theend-on phase shifters 1 or the broadside phase shifters 41 or, ifnecessary, both sets of phase shifters, are adjusted until the alignmentdesired, as shown by indicators not illustrated, is obtained. If bothsets of phase shifters are to be adjusted it is immaterial which set isadjusted first. Adjustment of phase shifters 41 by knob 48 changes thedisc-shaped broadside space factor into a shallow cone having an apexangle a as may be seen by comparing Figs. 3A and 88. An adjustment ofphase shifters I by knob 48 changes the apex angle is of the end-oncone, as is apparent from an examination of Figs. 3A and 8C. Fig. 3Gillustrates, by way of example, two other positions designated bynumerals 88 and 10 of the end-on space factor or cone, two otherpositions designated by numerals." and E2 of the broadside space factorcharacteristic and four other positions designated by the numerals II ofthe cigar-shaped lobe 82 (or surface 6|). It will be noted that asteering adjustment made in one plane changes the steering range in theother plane, that is, an adjustment of the endon characteristic changesthe steering range for the broadside characteristic and vice versa. Thehorizontal range for the same vertical angle of reception increases asthe end-on cone apex angle 1) increases. Thus, in accordance with theinvention, the cigar-shaped lobe of the system of Fig. 3 may be aligned,by vertical and/or horizontal steering with any incoming wave directionor path regardless of the value of the angle ting. When used fortransmitting, the first detectors are omitted and the receivers 48 arereplaced by a transmitter.

Fig. 4 illustrates a. dual steering arrangement which in a sense is theconverse of the arrangement of Fig. 3. As in Fig. 3 the severaln'ondirectional antenna-counterpoise units 38 are arranged in arectangle. The connection between the units and the receiver are such,however, that the units form three broadside subarrays ll, 15 and IIarranged end-on instead of three end-on subarrays 40, ll and 42 arrangedin broadside, as illustrated in Fig. 3. The broadside phase shifters 41are arranged in the two groups I! and II, the right-hand, center andleft-hand phase shifters 41 in these groups being connected,respectively, to the units constituting subarrays ll, 18 and II. Thethree subarrays are connected by means of conductors 43 to the commonsecond detector in receiver 48. A first detector (not illustrated) ispreferably inserted between each coaxial line '4 and the associatedsingle conductor line 5, a phase shifter I being included in all exceptone of the conductors 43. Phase shifters I and 41 ar controlled,respectively, by the uni-control knobs 48 and 49.

The method of alignment of the cigar-shaped lobe of the array of Fig. 4is the same as that described above in connection with Fig. 3. Inreality, however, the space factor directive characteristics of thethree broadside subarrays are simultaneously steered by means of knob 40to shifters are employed in the systems illustrated by Figs. 3 and 4.Figs. 3A, 3B, 3C, 3]), 3E and BF are applicable to the system of Fig. 4as well as to the system of Fig. 3. Directive antenna units,

of course, may be employed in the system of Figs. 3 and 4 instead of thenon-directive units 38, for the purpose of securing a more satisfactoryresultant lobe. For example, Fig. 5 illustrates an array comprisingrhombic units which may be substituted for the array shown above theline X-X in each of Figs. 3 and 4. When directive units are used thedirectional characteristic or the system lobe equals the product of thebroadside space factor characteristic, the end-on space factorcharacteristic and the directive characteristic of the unit, as isindicated by Figs. 5A, 5B, 5C and 5D.

Referring to the solid characteristic illustrated by Fig. 5A and thecross-sectional views by Figs. 53, 5C and SD of the solidcharacteristic, reference numeral 19 designates the solid uni-directivewhale-shaped characteristic of each rhombic an tenna, the rhombics beingpositioned so that their lobes each include the normal operating greatcircle and azimuthal wave cluster ranges. Numeral 62 denotes thecigar-shaped lobe (also illustrated in Fig. 3A) derived from the twospace factors and numeral 30 illustrates the product of resultant lobest2 and it, when the system is adjusted for alignment with direction be,included in the great circle plane XOZ at an angle 8| with thehorizontal. The lobes 62; and as may be steered as indicated by thedotted line representation of these lobes, vertically for alignment withanother direction, such as direction $2 included in the great circleplane or horizontally for alignment with another direction having thesame elevation angle at as, for example, direction 83 orbothhorizontally and vertically for alignment with astill differentdirection $51.

The view of Fig. 5B taken on the vertical or great circle plane X02 andthe view Fig. 5C taken on the oblique plane LlViOPQ are believed to beself-explanatory. Fig. 51) illustrates a view looking along axis 63toward the origin 0. It may be noted that the vertical plane andazimuthal steering range of the resultant lobe are dependent upon thesize and shape of the cross-sectional area of the unit lobe 19 asindicated in Fig. 5D.

Referring to Fig. 6, the antennamounterpoise units 38 are arranged oneabove the other in the same vertical plane to form a "stack" array. Theunits may be oriented for utilization of either horizontally polarizedor vertically polarized waves and if desired. directive units may beemployed in place of the non-directive units. As in Fig. 1, the unitsare connected by means of lines 3, d and 5 to the receiver, all exceptone of the lines 5 being equipped with a phase shifter i. Also, as inFig. 1, the phase shifters are adjusted by means of knob 9 throughuniformly graded gears II and equal size gears l2.

Assuming each unit antenna in the system of Fig. 6 is a horizontaldoublet positioned perpendicular to the great circle plane, the usefulunit directive characteristic above ground in the above plane is asemicircle as shown by the perspective view Fig. 6A and theverticalplane view Fig. 6C; and it is a figure 8 in the azimuthal plane as shownby Fig. 6A and the horizontal plane view, Fig. 6B. The space factorcharacteristic is a hollow cone or having a vertical axis 88 and a wall89. The unit characteristic and cone combine to produce the resultantcone 9B which is aligned with direction 9|. The common apex angle 0 ofthe two cones c1 and 9t! may be changed by means of knob 9 and phaseshifter I, whereby vertical steering over a maximum range (180 degrees)in any azimuthal plane is provided. In Fig. 60 the cone shown in dottedlines illustrates the position of the space factor characteristic whenit is aligned with direction 92. Of course, the space factorcharacteristic of the stack array is affected by the presence of theground surface, the amount being related to the height of the arrayabove the ground. This factor must be taken into account in actualpractice, in accordance with the manner well known in the art.

Fig. 7 illustrates a two-point long range communication system,reference numerals 98 and $6 designating, respectively, a transmissionstation and a receiving station widely separated therefrom as, forexample, a transmitting station located in England and a receivingstation located in the United States. In such a long range system, ithas been found that the maximum wave directive changes in the azimuthalplane occur relatively infrequently, that is, every several hours,whereas the maximum wave directive changes in the great circle planeconnecting the cooperating stations occur frequently, that is, every fewminutes. Consequently, and as illustrated by Figs. 7A and '13, anantenna system having a wide range steerable characteristic in theazimuthal plane and a fixed great circle directive range $6 may beemployed at the transmitting station; and an antenna system having afixed azimuthal directive range or and a wide range steerablecharacteristic $38 in the vertical or great circle plane may be employedat the re-" ceiving station. To illustrate, at the transmitter anantenna system 99 such as illustrated by Fig. 1 and at the receiver anantenna system I08 such as illustrated by Friis Patent 2,041,600 02Figs. 2 or 6 of the present application, may be employed. Preferably, apilot transmitter iiii having a non-directive or wide azimuthal range W2is used at the transmitting station and an azimuthal direction finder W3is employed at the receiving station In operation, the pilot transmitterit'll energizes all the normal azimuthal paths connecting the two widelyseparated stations and the receiver control operator determines by meansof the direction finder the azimuthal direction of the maximum wave i.The transmitter control operator then steers the direction of greatesttransmission of the main high power transmitter 93 so as to coincidewith the optimum prevailing azimuthal path asv indicated to him over apilot channel by the receiver control operator, and the receiveroperator adjusts the characteristic of the receiving antenna 91 so thatits direction of maximum action is aligned with the optimum great circlepath of the wave.

Although the invention has been disclosed .in connection with certainspecific embodiments, it should be understood that it is not to belimited to these embodiments since other apparatus and equipment may besatisfactorily employed without exceeding the scope of the invention.What is claimed is:

l. A method of radio communication between two stations,'utilizing atone station-a'transmitting system comprising an antenna having arelatively large flxedvertical directive range and means for steeringthe azimuthal plane direction of maximum action of said antenna over agiven range and, at the other station, a receiving eyetem comprising anantenna having a relatively large fixed azimuthal directive range andmeans for steering the vertical plane direction oi maximum action ofsaid antenna, which comprises positioning the transmitting and receivingantennas so that their azimuthal directive ranges station an antennaarray having in difierent planes movable directions of maximum action,which comprises aligning at the transmitting station the direction, insaid first-mentioned given plane, of maximum radiant action of saidtransmitting array with the optimum transmission path in said plane, andaligning at the receiving station the directions of, maximum radiantaction of said receiving array, in said different planes, with saidpath.

3. A method of communication utilizing an antenna array comprising aplurality of antenna subarrays spaced in a given direction and eachcomprising a plurality of antenna units spaced in another direction,said array and said subarrays each having a. unidirectional space factorcharacteristic, and means for moving the space factor directivecharacteristic of each subarray and for moving the space factordirective characteristic of the array, which comprises adjusting thecharacteristic of each subarray to include the same path and adJustingthe characteristic for the array to include the same path.

4. A method of radio communication between two stations, utilizing atthe receiving station an antenna array comprising a plurality ofdirective antenna units and having two independently adjustable spacefactor directive characteristics each characteristic having a. directionof maximum radiant action, the axes of said space factor characteristicsbeing perpendicularly related in the horizontal plane, which comprisespositioning the units so that their directive characteristics or lobesinclude the normal azimuthal and vertical plane incoming directiveranges of the waves propagated by the transmitting station, and aligningthe direction of maximum radiant action of each space factorcharacteristic with the direction or path of the strongest incoming waveincluded in said ranges.

5. A method of communication which comprises transmitting energy from atransmitting station to a receiving station equally along a large numberof different paths in the same plane, ascertaining at the receivingstation the path of the maximum incoming wave, transmitting from thetransmitting station a maximum amount of energy along the ascertainedpath, and receiving energy at the receiving station propagated alongonly the ascertained path, substantially.

6. In a. two-point communication system, a

transmitting station comprising a directive antenna array having asteerable azimuthal maximum direction of action and a relatively widevertical directive range, a receiving station cooperating with theflrst-mentioned station and comprising a directive antenna having avertical plane steerable direction of maximum action and a relativelywide fixed aximuthal directive range,

the maximum azimuthal directions of action of said transmitting andreceiving antennas being directed toward each other, substantially.

'7. In combination, an. antenna system comprising at least three antennaunits two of which are positioned in a broadside array and two in anend-on array, means for moving the directive characteristic of theend-on array and means independent thereof for moving the directivecharacteristic of the broad-side array.

8. In a two-point radio system, a transmitting station comprising abroad-side directively steerable antenna array, a receiving stationcomprising an end-on directively steerable antenna array, saidbroad-side array having its axis perpendicularly related to the greatcircle plane containing said stations and said'end-on array having itsaxis included in said plane.

9. In combination, a radio antenna array comprising a plurality ofantenna subarrays spaced in a given direction and each comprising aplurality of antenna units spaced in another direction, said array andsaid subarrays each having a space factor directive characteristic,means for simultaneously moving the space factor directivecharacteristic of each subarray, and

means for moving the space factor directive characteristic of the entirearray.

10. A two dimensional antenna array comprising'antenna units spacedalong two angularly related directions or axes, a plurality of phaseshifters, a translation device, said units being connected throughseparate phase shifters to said device whereby said array has a pair ofspace factor directive characteristics each related to a different arrayaxis, said characteristics being positioned so that portions thereofcoextend in space and are aligned with the optimum path of wavepropagation. I

11. In combination, a two-dimensional antenna array comprising at leastfour antenna units arranged to form with respect to a given verticalplane of wave propagation a pair of parallel endon subarrays and a pairof broad-side subarrays, each subarray comprising at least two spacedantenna units, a plurality of phase shifters, a. translation deviceconnected to all said units, a. first phase shifter being includedbetween the device and all the units in one subarray, a second phaseshifter being included between said first phase shifter and one of thelast-mentioned units, and a third phase shifter included between saiddevice and an antenna unit in the other similar subarray.

12. In combination, a translation device, a stack antenna arraycomprising a plurality of antenna units arranged one above the other,and means comprising individual phase shifters connecting said units tosaid device for obtaining a steerable space factor characteristic forsaid array, whereby a vertical steering range including high elevationangles is obtained.

\ CARL B. H. F'EIDMAN.

HARALD T. FRIIS.

